How to know which object is using a material
The outliner is a great place to find things. Entering a string in search field located in the header not only finds items containing the string but highlights them for easy access. The search menu also offers choices for case sensitive and complete matches.



Many things can be found in the outliner - from objects and meshes to materials, textures, modifiers, vertex groups, constraints, bones and actions.

While image names used by blender internal textures can be searched, currently images used in nodes (internal or cycles) can't.